Direct or indirect contact with bird allergens may cause sensitisation. Bird allergens may be major components of house dust.

Allergen Exposure

Geographical distributionThe Canary is one of the most common domestic birds, together with Budgerigars and Parrots. In 1994, these birds were estimated at 25 million in US households, and more than 8 millions in German ones (1).

These birds descend from the wild Serin Finch or the very similar Wild Canary, and their ancestors were brought from the Canary Islands, Madeira, or the Azores. The Wild Canary, which still exists, is brownish green and looks like a Sparrow. Captive breeding has gone on for 500 years, during most of which time Canaries were the most popular cage birds in the world, because of their singing and mimicry and the ease with which they breed in captivity. The yellow mutation (with the bird remaining the size and shape of a Finch) has been the most popular, but Canaries are available in many colors and a range of sizes, shapes, patterns and songs. The German (or Hartz Mountain) Roller is the classic song Canary and was the most numerous Canary breed in the world for many years. The American Singer is a newer song breed that was developed in the United States. Usually somewhat aloof in nature, they do not typically bond to people.

EnvironmentSee above.

AllergensWell-defined major allergenic bands with molecular mass of 20-30 kDa and 67 kDa have been detected and identified in IgE immunoblots with feather extracts as well as with serum proteins of Budgerigar, Parrot, Pigeon, Canary, and Hen. Inhalable feather dust was shown to contain several allergenic components which cross-react with serum allergens/antigens of the same as well as of other bird species (1). The allergens have not been fully characterised yet.

Potential Cross-Reactivity

As noted above, inhalable feather dust contains several allergenic components which cross-react with serum allergens/antigens of the same as well as of other bird species (1).

Cross-reactivity between Canary and other phylogenetically related bird species may be expected, and in Canary-allergic patients, significant IgE antibody titers to Parrot, Budgerigar, Chicken, Pigeon, Goose and Duck have been reported (2-3), en in patients without known exposure1. Moreover, cross-reactivity to Hen's egg, Bird-Egg Syndrome, should be considered,. Here the livetins present in egg yolk have been suggested as the major cross-reacting allergen (4-5). This adult type of egg intolerance must be distinguished from the common egg-white allergy of atopic children.

Clinical Experience

IgE-mediated reactionsAsthma, allergic rhinitis and allergic conjunctivitis may result following exposure to Canary feathers, epithelial cells or droppings (6). The allergic manifestations may present as Bird Fancier´s Asthma and as Bird-Egg Syndrome, with symptoms such as rhinitis, urticaria and angioedema (2) and also as gastro-intestinal problems (3). Specific IgE has been found in patients exposed to Canary (1-3) (6).

In a study, IgE antibodies to Canary were present in about 25% of the bird fanciers investigated (6). Among 212 sera from Budgerigar and Canary fanciers with symptoms of rhinitis and/or bronchial asthma, in 25 of 98 Canary feather-specific IgE antibody measurements, a significant level of specific IgE was found. In 3 sera IgE antibodies against sera from both birds were present. Canary feathers were shown to contain IgE-binding antigens that were not present in the bird sera and droppings (6).

In a prospective study, 258 adults were investigated for sensitisation against bird antigens (Budgerigar, Canary, Pigeon) using an intracutaneous test. Thirty (38%) showed a positive skin reaction with at least 1 of the 3 extracts tested. In persons not exposed to birds, 24/96 (25%) were found to react to at least one of the three allergen extracts (7).

Extrinsic allergic alveolitis, also known as hypersensitivity pneumonitis, Bird Fancier's Lung and Farmer's Lung, is a disease of inflammation of the lung parenchyma in the terminal bronchioles and alveoli. Symptoms may start soon after exposure to bird allergens or after many years, and may include breathlessness, cough, occasional chills, and fever. Death may also result.

The disease occurs after exposure to organic dust, especially after close contact with Pigeons or other birds such as Budgerigars, Parrots, Canaries, Parakeets, Cockatiels, Doves and Finches. Exposure results in the development of immunoglobulin antibodies including IgE (1), IgM (8), IgA and various IgG subclasses (9) (10-11). The antibodies may be found in the sera and saliva of patients (12) as well as in the sera of asymptomatic but exposed subjects (13).

The allergenic proteins may be found in bird serum, droppings, skin scales, feathers and, in the case of Pigeons, Pigeon bloom (a waxy fine dust which coats the feathers of Pigeons). Contact may result from handling birds, cleaning their lofts, or exposure to the organic dust drifting down from a ceiling or roof where birds nest.

This is typified in a report of a 54-year-old man who presented with features consistent with extrinsic allergic alveolitis occurring after contact with his pet birds (14).

Diagnosis is based on a characteristic clinical picture and a typical x-ray pattern, accompanied by the presence of specific IgG antibodies (15).

The measurement of specific IgG using IgG tracer technology has been shown to be a sensitive and specific assay for the routine diagnostic testing of extrinsic allergic alveolitis (16).